The ultimate goal of this project is the elucidation of the mechanisms controlling the overall rate of protein synthesis in mammalian tissues. Present work is concentrating on the mechanisms modulating the rate of peptide chain initiation in the Ehrlich ascites tumor cell growing in suspension culture, in response to nutritional deprivation (omission of glucose, an essential amino acid, or serum from the medium). We are investigating the steps and components involved in the binding of Met-tRNAf to the native 40s ribosomal subunit, and alterations in these factors during nutritional stresses.